Context- Patients with gastrointestinal cancers are at high risk for functional problems that are generally accompanied by a decline in their overall status and intense psychological distress. Objectives- This study compares the level of functioning in individuals with gastric cancer (GC) and colorectal cancer (CRC) and analyzes whether improved functioning can be explained by patients' psychological status and coping strategies. Methods- Prospective, transversal, multicenter study in patients with non-metastatic GC and CRC prior to initiating adjuvant chemotherapy. Participants answered questionnaires evaluating quality-of-life, including functioning (EORTC-QLC-C30), coping strategies (Mini-MAC), and psychological distress (BSI-18). Results- Between December 2015 and July 2017, 266 patients with CRC and 69 with GC were consecutively recruited. A pathological level of functioning was more prevalent in people with GC than CRC (20% vs. 5%). Individuals with GC presented worse functioning and more psychological distress and displayed more hopelessness, anxious preoccupation, and cognitive avoidance as coping strategies than those with CRC. Psychological distress and fighting spirit accounted for 40% of the functional status in GC patients, whereas psychological distress and hopelessness represented 58% of CRC patients' functional status. Conclusion- Our findings suggest that level of functioning affects many subjects with GC and reveals the importance of developing interventions targeted at enhancing adaptive coping strategies before initiating adjuvant cancer treatment.